|Speed [km/h (mph)]|Train|Type|Location|Date|Comments|
|---|---|---|---|---|---|
|504 (313.2)|ML-500|Maglev|Miyazaki Maglev Test Track|12 December 1979||
|517 (321.2)|ML-500|Maglev|Miyazaki Maglev Test Track|21 December 1979||
|352.4 (219.0)|MLU001|Maglev|Miyazaki Maglev Test Track|January 1986|Three-car train set|
|405.3 (251.8)|MLU001|Maglev|Miyazaki Maglev Test Track|January 1987|Two-car train set|
|431 (267.8)|MLU002N|Maglev|Miyazaki Maglev Test Track|February 1994|Single-car|
|550 (341.8)|MLX01|Maglev|Yamanashi Maglev Test Line|24 December 1997|Three-car train set|
|548 (340.5)|MLX01|Maglev|Yamanashi Maglev Test Line|18 March 1999|Five-car train set|

Question: how many cars were in the set for the december 24, 1997 record?
Answer: 3